A carrier tape is commonly used for transporting electronic components such as IC. Namely, such electronic components are inserted in recesses for accommodating the electronic components, formed at prescribed distances on a carrier tape, and a cover tape having a readily peelable adhesive layer on a substrate, is heat-sealed on the upper side of the carrier tape thereby to seal in the electronic components, followed by being wound up and transported in a reel state. Such a cover tape is required to be transparent to such an extent that such electronic components can be inspected, and it is required to be easily and smoothly peeled from the carrier tape. Further, in a case where such electronic components are components susceptible to dielectric breakdown by static electricity, antistatic treatment is applied to one side or both sides of the cover tape to prevent deposition of dust or to protect the contents from static electricity, or to prevent such a trouble that when the cover tape is peeled from the carrier tape, such electronic components pop out as adhered to the cover tape.
For such antistatic treatment, a method may be employed wherein an antistatic agent is incorporated to a resin constituting the surface to be provided with an antistatic property, or a method wherein an antistatic agent is applied to such a surface. One having an antistatic agent applied to the surface of an adhesive layer is disclosed, for example, in Patent Documents 1 to 4.
By such methods, it is possible to obtain an antistatic effect. However, if a large amount of an antistatic agent is applied in order to obtain a sufficient effect, the sealing strength to the carrier tape tends to be unstable. Further, if left in a high temperature and high humidity environment, a metal portion of e.g. IC as the content is likely to be corroded. If a non-ionic antistatic agent is employed as the antistatic agent, the above-mentioned corrosion of the metal portion may decrease, but even in such a case, a very small amount of ions will be present, and depending upon the environmental conditions, corrosion of the metal portion tends to result, and an improvement in this respect has been desired.
On the other hand, a method has also been proposed wherein as the adhesive layer, fine particles of conductive metal are mixed to a thermally adhesive resin (e.g. Patent Documents 5 and 6). However, by such a method, the transparency of the cover tape deteriorates, thus leading to a problem that it becomes difficult to identify the shape, etc. of the content. Especially in a method of inspecting electronic components such as IC in recent years in which a defect such as a deformation of a pin of IC is photographed by a CCD camera from above the cover tape, followed by image analysis for its detection, the requirement for the transparency of the cover tape is increasingly high.
Patent Document 1: Japanese Patent 2901857
Patent Document 2: JP-A-11-115088
Patent document 3: JP-A-7-172463
Patent Document 4: JP-A-2001-171727
Patent Document 5: JP-A-7-251860